By the mid-20th century, water in the West served cities, private industries, military bases, and irrigation as well as agriculture. Droughts during the 1930s showed that Rapid City could not rely on surrounding springs for a municipal water supply, and when the War Department broke ground on Ellsworth Air Force Base northeast of the city in 1942, the additional 5,000 military personnel further strained the city's limited water resources. Pressure on those resources, along with the need for irrigation water, led local leaders to seek help from Reclamation. The federal response was the construction of Deerfield Dam in 1945 and Pactola Dam in 1952. The Rapid Valley Unit consists of Pactola Dam and Reservoir on Rapid Creek, while the Rapid Valley Project includes Deerfield Dam and Reservoir on Castle Creek, an upstream tributary to Rapid Creek. The unit is part of the Pick-Sloan Missouri Basin Program, a comprehensive water development plan for the Missouri River basin created in 1944. Together, the two reservoirs provide supplemental irrigation water for 8,900 acres of farmland in the Rapid Valley Water Conservancy District, municipal and industrial water for Rapid City including Ellsworth Air Force Base, flood control benefits for Rapid City and areas along Rapid Creek, and recreation and fish and wildlife benefits through cooperative efforts between Reclamation and other federal and state agencies.